Experimental uncertainty and measurement, particularly in engineering, have been increasingly emphasized over the last 20 years. Uncertainty analysis of ship model testing in seakeeping experiments based on International Organization for Standardization, Guide for Uncertainty of Measurements (ISO-GUM), report with recommendations published by ITTC (2008). In this paper, the uncertainties for free-running tests were performed for a model scale 1:62 as a benchmark model test at the Indonesian Hydrodynamic Laboratory (IHL). The benchmark model is representative of a full scale of 186 meters. The model has full appendages as well as a rudder and propellers to allow for free-running tests, natural roll period, free roll decay, and swing tests. Factors of basic uncertainty (type A and type B) are estimated using model tests. The standard deviation of the mean value of a repeated measurement is uncertainty type A. However, Type B uncertainty is estimated from manufacturing specifications. The uncertainty components resulting from both types are quantified by standard deviations. The uncertainty value of Type B is approximated by a corresponding variance. This study helps to understand the underlying uncertainty associated with this research, which resulted in a total geometry uncertainty value (Lpp, B, T, H, KG ¯ , and kyy) of 0.17598% and the total uncertainty value of the instrument calibration results (wave height sensor and qualysis motion tracking) is 0.01161%. The results of this study are expected to minimize the impact of sources of uncertainty and allow the potential for underlying uncertainty to be corrected for the next seaworthiness test.

Confidence levels of the seakeeping experiment results can be assessed through uncertainty analysis. The seakeeping experiments with a free-running model system were carried out in the manoeuvring and ocean engineering basin (MOB) at the Indonesian Hydrodynamic Laboratory (IHL) using uncertainty techniques to improve the experiment quality. The method used is the International Organization for Standardization, Guide for Uncertainty of Measurements (ISO-GUM), type A and B uncertainty, which is the foundation for the uncertainty analysis for seakeeping experiment recommendations released by the International Towing Tank Conference (ITTC). This research aims to determine the combined uncertainty value of the seakeeping experiment on a benchmark ship model with a scale of 1:62, representing the full scale of 186 meters. Seakeeping testing is carried out under head and beam waves, each with regular waves at one wave height (Hs) with three different wave periods (Tw). The experimental seakeeping result, generally, has the same tendency in each heave, pitch, and roll motion mode. The expanded uncertainty with 95% confidence level of the RAO-Heave uncertainty in all period conditions is always less than 3%, RAO-Pitch uncertainty in all period conditions is always less than 1%, and RAO-Roll uncertainty in all period conditions is always less than 1.2%. These uncertainties are quite small.

Perkembangan energi terbarukan mengalami peningkatan pesat seiring menipisnya cadangan bahan bakar fosil. Arus laut adalah sumber energi terbarukan yang memiliki potensi besar di Indonesia namun didominasi oleh kecepatan arus rendah. Vertical Axial Tidal Current Turbine (VATCT) adalah teknologi yang cukup efektif mengkonversi energi arus laut rendah menjadi energi listrik. NACA 63(4)021 adalah jenis hidrofoil yang sedang trend digunakan karena dapat menghasilkan efisiensi yang lebih baik. Oleh karena itu, dilakukan studi numerik hidrofoil NACA 63(4)021 berdasarkan kondisi kecepatan arus rendah. Studi numerik menggunakan model 2D dengan variasi sudut serang dan initial condition Re 200.000. Dari hasil studi, diketahui nilai Cl maksimal 1,16 pada AoA 15?, sedangkan nilai Cd cukup rendah pada AoA antara 0? hingga 10?. Nilai Cl/Cd maksimal adalah 25.5 pada AoA 8?. Dengan demikian, direkomendasikan sudut ideal hidrofoil NACA 63(4)02 pada VATCT adalah 8? (untuk turbin fixed pitch) atau pada rentang sudut 5? hingga 10? (untuk turbin active-passive pitch).